Fans of Lady Gaga. Little Monsters are loyal to Lady Gaga, buy her singles, t-shirts, posters, you name it. Another name for Little Monsters are 'Super Fans' named by Lady Gaga herself for fans who would literally do anything for her.

Little Monsters often name themselves after her on twitter or tumblr and sometimes even insert it into their facebook name.
e.g. Twitter: '@NameGaga'
e.g. Tumblr: 'www.BornThisWay.tumblr.com
e.g. Facebook:'Name 'gaga Surname

Little Monsters go crazy at concerts of Lady Gaga and have been known to feint, cry and scream in hysterics. They often create fan mail/ letters/ flags and throw them on stage for 'Mother Monster.

The Urban Dictionary T-Shirt

What Lady Gaga calls her fans.
Little monsters are more than just fans though, they are the people who have twitter accounts supporting Gaga, have lots of Gaga merch and really love gaga.
They know almost everything about her and most importantly they have heard more than just her big hits, they know all her songs even from before she was famous.
They put their hand up in a claw form when Gaga says "Paws Up". They were born this way!
They also call each other "hooker, whore, bitch, etc" just cause they love each other. They are like a big family rather than just a fan base.